The main constituent of biogas is :

Options

A. methane
B. carbon dioxide
C. hydrogen
D. hydrogen sulphide

Explanation

To determine the main constituent of biogas, we need to analyze the composition of biogas and identify which gas has the highest percentage contribution.

### Step-by-Step Solution:

1. **Identify the Components of Biogas**:
Biogas is primarily composed of several gases, including methane (CH₄), carbon dioxide (CO₂), hydrogen sulfide (H₂S), and traces of other gases.

2. **Determine the Percentage Contributions**:
- Methane (CH₄): Approximately 25%
- Carbon Dioxide (CO₂): Approximately 23%
- Hydrogen Sulfide (H₂S): Approximately 2%
- Other gases: Negligible amounts

3. **Compare the Percentages**:
To find the main constituent, we compare the percentage contributions of each gas.
- Methane: 25%
- Carbon Dioxide: 23%
- Hydrogen Sulfide: 2%

4. **Identify the Main Constituent**:
From the comparison, we can see that methane has the highest percentage contribution (25%) among the listed components.

5. **Conclusion**:
Therefore, the main constituent of biogas is methane (CH₄).

### Final Answer:
The main constituent of biogas is methane (CH₄).